This invention relates to a polyester composition and a support for photography, more particularly to a support for photography having a polyester layer comprising a polyester composition containing a titanium dioxide.
In photographic materials for direct observation of photographic images, as their supports (opaque supports), resin-coated raw papers (RC raw papers) have been generally used in the art, but in recent years, there have been also used white resin films opacified by filling with white pigments such as barium sulfate, titanium dioxide, etc. as disclosed in Japanese Patent Publications Nos. 4901/1981, 30930/1985, or Japanese Unexamined Patent Publication No. 118746/1986. Also, a film which has been made translucent with the amount of the white pigment being made small has been also used for light-sensitive materials for use in both the reflection type and the transmission type to be used particularly for display, etc.
However, of these supports, still no sufficient whiteness has been obtained for those by use of titanium oxides under the present situation. Particularly, a white film comprising a polyester filled with a titanium dioxide as seen from the above-mentioned Japanese Unexamined Patent Publication No. 118746/1986 may be preferably used as the support for giving photographic images excellent in sharpness, but for giving sufficient opaqueness to such polyester filled with titanium dioxide, it is required to fill 10 % by weight or more of titanium dioxide. In the prior art, as the method for adding titanium dioxide into polyester, there are the method in which a slurry having titanium dioxide dispersed in a polyhydric alcohol such as ethylene glycol, etc. is added to a polyester polymerization system, and the method in which titanium dioxide is kneaded into a polyester polymer by means of a kneading machine such as biaxial kneader, etc. However, among these, in the above-mentioned polymerization system addition method, titanium dioxide tends to be precipitated by agglomeration in the polyhydric alcohol, and it is extremely difficult to add 10% by weight or more of titanium dioxide to the polymer which has been completely polymerized. Further, in said method, the surface of said titanium dioxide is required to have hydrophilicity for dispersing the titanium dioxide into the polyhydric alcohol, but because the polyester polymer has no such hydrophilicity, titanium dioxide tends to be agglomerated in the polymer. Such agglomeration of titanium dioxide may cause undesirably breaking during film fabrication, or generate unevenness in the film fabricated. Therefore, as the method for adding titanium dioxide to the polyester, the above-mentioned polymer kneading method which can fill a large amount of titanium dioxide with good dispersibility has been preferably used.